Posttraumatic stress disorder is one of the most common psychiatric disorders with a lifetime prevalence of 7.8%. PTSD is often comorbid with other disorders especially sleep disturbances such as nightmares and insomnia. In fact, sleep disturbances are considered characteristic and predictive of PTSD. The main objective is to identify treatment for insomnia related to PTSD. Both PTSD and insomnia are associated with chronic activation of the sympathetic nervous system or hyperarousal. Yoga, due to its ability to reduce physiological arousal, may significantly reduce insomnia in PTSD patients as well as the severity of PTSD. Preliminary data on yoga for sleep disturbances has shown that yoga reduces primary insomnia. In addition, other studies with PTSD patients have found reduction in PTSD symptoms following yoga interventions. The proposed research is an innovative therapeutic use of yoga as an intervention for people with insomnia and PTSD. There are three specific aims: to evaluate if yoga reduces insomnia by improving subjective sleep quality in PTSD patients; to evaluate if yoga reduces insomnia by improving objective sleep quality in PTSD patients; and to test if this intervention also reduces PTSD symptom severity and relationships with sleep outcomes. The specific aims will be accomplished using a randomized controlled pilot study of an eight - week yoga treatment for insomnia in PTSD patients. Because yoga has become increasingly practiced and utilized in self-care especially PTSD symptom management, this research training plan is aligned with the NCCAM mission to explore widely used complementary and alternative practices with scientific rigor.